备份现有apt源配置

mv /etc/apt/sources.list /etc/apt/sources.list.old​

替换源
替换为默认官方源

# 全部复制后，直接粘贴并按下回车执行
cat > /etc/apt/sources.list << EOF

deb http://deb.debian.org/debian/ bullseye main contrib non-free
deb-src http://deb.debian.org/debian/ bullseye main contrib non-free
 
deb http://deb.debian.org/debian/ bullseye-updates main contrib non-free
deb-src http://deb.debian.org/debian/ bullseye-updates main contrib non-free
 
deb http://deb.debian.org/debian/ bullseye-backports main contrib non-free
deb-src http://deb.debian.org/debian/ bullseye-backports main contrib non-free
 
deb http://deb.debian.org/debian-security/ bullseye-security main contrib non-free
deb-src http://deb.debian.org/debian-security/ bullseye-security main contrib non-free
EOF

替换为腾讯云内网源

cat > /etc/apt/sources.list << EOF
deb http://mirrors.tencentyun.com/debian/ bullseye main contrib non-free
deb-src http://mirrors.tencentyun.com/debian/ bullseye main contrib non-free
 
deb http://mirrors.tencentyun.com/debian/ bullseye-updates main contrib non-free
deb-src http://mirrors.tencentyun.com/debian/ bullseye-updates main contrib non-free
 
deb http://mirrors.tencentyun.com/debian/ bullseye-backports main contrib non-free
deb-src http://mirrors.tencentyun.com/debian/ bullseye-backports main contrib non-free
 
deb http://mirrors.tencentyun.com/debian-security/ bullseye-security main contrib non-free
deb-src http://mirrors.tencentyun.com/debian-security/ bullseye-security main contrib non-free
EOF

替换为阿里云内网源

cat > /etc/apt/sources.list << EOF
deb http://mirrors.cloud.aliyuncs.com/debian/ bullseye main contrib non-free
deb-src http://mirrors.cloud.aliyuncs.com/debian/ bullseye main contrib non-free
 
deb http://mirrors.cloud.aliyuncs.com/debian/ bullseye-updates main contrib non-free
deb-src http://mirrors.cloud.aliyuncs.com/debian/ bullseye-updates main contrib non-free
 
deb http://mirrors.cloud.aliyuncs.com/debian/ bullseye-backports main contrib non-free
deb-src http://mirrors.cloud.aliyuncs.com/debian/ bullseye-backports main contrib non-free
 
deb http://mirrors.cloud.aliyuncs.com/debian-security/ bullseye-security main contrib non-free
deb-src http://mirrors.cloud.aliyuncs.com/debian-security/ bullseye-security main contrib non-free
EOF

更换为清华源

cat > /etc/apt/sources.list << EOF
# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb http://mirrors.tuna.tsinghua.edu.cn/debian/ bullseye main contrib non-free
deb-src http://mirrors.tuna.tsinghua.edu.cn/debian/ bullseye main contrib non-free

deb http://mirrors.tuna.tsinghua.edu.cn/debian/ bullseye-updates main contrib non-free
deb-src http://mirrors.tuna.tsinghua.edu.cn/debian/ bullseye-updates main contrib non-free

deb http://mirrors.tuna.tsinghua.edu.cn/debian/ bullseye-backports main contrib non-free
deb-src http://mirrors.tuna.tsinghua.edu.cn/debian/ bullseye-backports main contrib non-free

deb http://mirrors.tuna.tsinghua.edu.cn/debian-security bullseye-security main contrib non-free
deb-src http://mirrors.tuna.tsinghua.edu.cn/debian-security bullseye-security main contrib non-free

# deb http://security.debian.org/debian-security bullseye-security main contrib non-free
# deb-src http://security.debian.org/debian-security bullseye-security main contrib non-free
EOF

运行更新

sudo apt update #更新源
sudo apt upgrade #更新已安装的包
sudo apt dist-upgrade #升级系统
sudo apt clean && sudo apt autoclean #清理下载文件的存档